While the present invention can be used in any circuit board where one component or package is connected to another component or package, it will be described for clarity in reference to xerographic or electrostatic marking systems. The use of ball grid array (BGA) is well known in the printed circuit board assembly (PCBA) art. The literature describes BGA structures as follows:
The BGA is descended from the pin grid array (PGA) which is a package with one face covered (or partly covered) with pins in a grid pattern. These pins are used to conduct electrical signals from the integrated circuit to the printed circuit board (PCB) it is placed on. In a BGA, the pins are replaced by balls of solder stuck to the bottom of the package. The device is placed on a PCB that carries copper pads in a pattern that matches the solder balls. The assembly is then heated, either in a re-flow oven or by an infrared heater, causing the solder balls to melt. Surface tension causes the molten solder to hold the package in alignment with the circuit board, at the correct separation distance, while the solder cools and solidifies. The BGA is a solution to the problem of producing a miniature package for an integrated circuit with many hundreds of pins. Pin grid arrays and small-outline integrated circuit (SOIC) packages were being produced with more and more pins, and with decreasing spacing between the pins, but this was causing difficulties for the soldering process. As package pins got closer together, the danger of accidentally bridging adjacent pins with solder grew. BGAs do not have this problem, because the solder is sometimes factory-applied to the package in exactly the right amount.
In high speed marking systems, speed of the system and space of structures used in the apparatus are very important considerations. Faster speed processors require that the connectors or signal traces be made shorter and at the same time, provide reliable signal traces lengths between packages. Sometimes in the prior art, the inductance in the longer signal traces blocks the signal; in high speed apparatus it is not acceptable to have blockage by an inductor. To minimize blockage, the present invention makes the length of the signal traces as short as possible and thereby minimizing the inductance.
A component on a printed circuit board is made up of a package which houses at least one silicone chip. Each package performs a specific function and each interacts with other packages by use of signal traces. For example, in a high speed copier coordinating the various processing stations exactly is not only desirable but is also necessary for proper functioning. A primary purpose of the present invention is to push the PCB architecture to a higher performance level by improving the time of package or component interaction with each other. The solder balls of the BGA are bonded on the bottom surface of the package and are the outer terminal of the package.
Coordinated ball grid array pairs are another way besides signal traces to provide connections between packages or components. The use of ball grid arrays in PCB are described in detail in U.S. Pat. Nos. 6,809,537B2 and 6,861,761 B2, the disclosures of these two patents are incorporated by reference into the present disclosure.